Copper-leaching process.



FREDERICK LAIST, CE BUTTE, MONTANA.

COPPER-REACHING PROCESS.

Specification of Letters Patent.-

Application filed April 16, 1908. Serial No. 427,306.

Patented Nov. 10, 19 08.

To all whom it may concern:

Be it known that I, FREDERICK LAIST, a citizen of the United States, residing at Butte, in the county of Silverbow and State of Montana, have invented a new and useful Improvement in Copper-Leaching Processes, of which the following is a specification.

The process relates to the leaching of oxidized copper ores with a dilute solution of sulfuric acid which contains chlorin in the form of a chlorid of some sort, (such as sodium chlorid, ferrous chlorid or calcium chlorid); in quantity suflicient to form the sub-chlorid with the copper which goes into the solution and it consists in the novel mode of procedure hereinafter described.

Having dissolved the copper from the ore, it is to be precipitated from the resultant solution as the sub-chlorid, or cuprous I chlorid, (Cu cl This is done preferably by running the cold solution down an absorbent tower up which sulfur dioxid gases,-

(generated by burning pyrites, sulfur, etc.,) are passing. The sulfur dioxid is absorbed by the cold solution, so that I obtain a solution containing 2% to 4% of sulfur dioxid. The percentage of sulfur dioxid gas absorbed must be at least one half of the per cent. of copper which the solution contains. This solution is now run into a boiler, lined with an acid proof metal, and containing steam coils for heating and a safety valve adjusted to go off at about 15 lbs. pressure.

Here it is brought to boiling and the'fol lowing reaction takes place.

or more simply stated I quantities of ore.

1 I am aware that the reactions of this process have been already described in patents later as the Hunt and Douglas process. My

invention is distinguished therefrom by the improved method of working, which consists in absorbing the sulfur dioxid in the cold copper solution and then heating under pressure to completethereaction between the sulfur dioxid and the cupric chlorid. The method they pursued was to inject sulfur dioxid into the hot copper solution. This method'is not nearly so economical of sulfur dioxid nor so convenient of manipulation as my method. Moreover the sulfur dioxid obtained in practice always contains some oxygen. Hence an oxidation of the precipitated cuprous chlorid always accompanies the reduction of the cupric chlorid which makes it impossible to obtain a complete conversion of the cop er into cuprous chlorid. In my method t is does not take place, since the oxygen comes in contact only with the cold solution and before the formation of cuprous chlorid has properly started.

Heating under pressure, very materially I aids the reduction, because it keeps the sulfur dioxid in the solutionuntil the reaction temperature, (which is near 100 C.) is reached. It is very difiicult to obtain a precipitation of more than 75% of the copper in the solution when heating in the open. Under pressure, 90% to 95% can be brought down. In fact the completeness of precipitation is limited only by the slight solubility of cuprous chlorid."

I claim The process of precipitating copper from a chloridiz'ed solution as the sub-chlorid, which consists in first dissolving inthe cold solution a quantity ofsulfur dioxid, and then heating this solution, under pressure, to complete the reduction of the cupr c chlorid to cuprous chlorid. Y

FREDERICK LAIST.

.Witnesses JAMES E. MURRAY, HOWARD K. WELCH. v 

